Update install-nfs-csi-driver.md

Author: andyzhangx

docs/install-nfs-csi-driver.md

@@ -1,6 +1,6 @@
 ## Install NFS CSI driver on a Kubernetes cluster
 
- - [install CSI driver master version](./install-csi-driver-master.md)
+ - [install CSI driver master version](./install-csi-driver-master.md)(only for testing purpose)
  - [install CSI driver v4.0.0 version](./install-csi-driver-v4.0.0.md)
  - [install CSI driver v3.1.0 version](./install-csi-driver-v3.1.0.md)
  - [install CSI driver v3.0.0 version](./install-csi-driver-v3.0.0.md)